We look at the division of 869665 by 81 
The aim is to understand the frequency of 81 in 869665.

Advancing to step 1:
8 divided by 81 is 0 with a remainder of 8.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 8, we get 8.
Fetch the next digit (6) from the dividend, attach it to 8 and continue: 86 / 81

Step 2:
81 goes into 86 1 times with a remainder of 5.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtract 81 from 86 to get 5.
Append the next digit (9) from the dividend to 5 and continue with: 59 / 81

On to step 3:
When dividing 59 by 81, we get 0 with a remainder of 59.
Write down 0 as next digit of the result. 
Result so far: 10.0
Subtracting 0 from 59 leaves us with 59.
Grab the next digit (6) from the dividend, add it to 59, then carry on: 596 / 81

Going ahead to step 4:
81 goes into 596 7 times with a remainder of 29.
The number 7 becomes the next digit in our result. 
Result so far: 107.0
Deduct 567 from 596 and we're left with 29.
Include the next digit (6) from the dividend after 29, then repeat: 296 / 81

Let's proceed to step 5:
296 divided by 81 is 3 with a remainder of 53.
Record the quotient 3 as the next digit in the result. 
Result so far: 1073.0
Subtracting 243 from 296 leaves us with 53.
Include the next digit (5) from the dividend after 53, then repeat: 535 / 81

Moving on to step 6:
81 can be fit into 535 6 times, resulting in a remainder of 49.
Write down 6 as next digit of the result. 
Result so far: 10736.0
Deduct 486 from 535 and we're left with 49.
Since there are no more digits in the dividend, we add a zero to the remainder making it 490, and continue the process.

Step 7:
If we divide 490 by 81, we get 6 and a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 10736.6
If we subtract 486 from 490, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

On to step 8:
The number 81 fits into 40 0 times, leaving a remainder of 40.
The number 0 becomes the next digit in our result. 
Result so far: 10736.6
Subtract 0 from 40 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Going ahead to step 9:
81 goes into 400 4 times with a remainder of 76.
The number 4 becomes the next digit in our result. 
Result so far: 10736.604
Subtract 324 from 400 to get 76.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Let's proceed to step 10:
81 can be fit into 760 9 times, resulting in a remainder of 31.
Use 9 as the next digit of our solution. 
Result so far: 10736.6049
If we subtract 729 from 760, we get 31.
Since there are no more digits in the dividend, we add a zero to the remainder making it 310, and continue the process.

On to step 11:
81 goes into 310 3 times with a remainder of 67.
The next digit of our result is 3. 
Result so far: 10736.60493
Subtract 243 from 310 to get 67.
Since there are no more digits in the dividend, we add a zero to the remainder making it 670, and continue the process.

Let's proceed to step 12:
81 can be fit into 670 8 times, resulting in a remainder of 22.
Use 8 as the next digit of our solution. 
Result so far: 10736.604938
Subtracting 648 from 670 leaves us with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

Step 13:
81 goes into 220 2 times with a remainder of 58.
Record the quotient 2 as the next digit in the result. 
Result so far: 10736.6049382
The remainder is 58 after subtracting 162 from 220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

On to step 14:
580 divided by 81 is 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 10736.60493827
If we subtract 567 from 580, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

In conclusion, the division gives 10736.60493827 with a balance of 1.3e-08.